Rotary harrows

ABSTRACT

A rotary harrow has a plurality of soil working members each of which has a support and a central shaft that forms the axis of rotation of said member. Each support has a holder at each end thereof and a downwardly extending tine secured in each holder. The holder is preferably inclined so that its top is located further from the central shaft than its bottom and also leads in the direction of normal rotation relative to the holder bottom. The holders are sleeves with integral screens and the sleeves receive the fastening portions of tines. The holders together with the support form tine mountings configured to minimize damage from stones and other debris. The tine fastening portions are held inclined to the vertical as well as soil working portions which are bent first towards one another then away, so that the lower tine tips are located further from the shaft axis than are the corresponding fastening portions. A forward, generally cylindrical support member protects the soil working members and supports the harrow frame.

According to one aspect of the invention, there is provided a rotaryharrow of the kind set forth, wherein the top of each holder is furtherspaced from the axis of rotation of the corresponding soil workingmember than is the bottom thereof at the side or end of that holderwhich faces away from said axis.

For a better understanding of the invention, and to show how the samemay be carried into effect, reference will now be made, by way ofexample, to the accompanying drawings, in which:

FIG. 1 is a plan view of a rotary harrow in accordance with theinvention connected to the rear of an agricultural tractor,

FIG. 2 is a section, to an enlarged scale, taken on the line II--II inFIG. 1,

FIG. 3 is an elevation as seen in the direction indicated by an arrowIII in FIG. 2,

FIG. 4 is a section taken on the line IV--IV in FIG. 3,

FIG. 5 is a part-sectional plan view, to an enlarged scale, illustratingthe construction and arrangement of three soil working members of theharrow of FIG. 1 in greater detail,

FIG. 6 is a section, to an enlarged scale, taken on the line II--II inFIG. 1 but illustrates an alternative construction of some parts of theharrow,

FIG. 7 is a plan view as seen in the direction indicated by an arrow VIIin FIG. 6,

FIG. 8 is a further section, to an enlarged scale, taken on the lineII--II in FIG. 1 but illustrates another alternative construction forsome parts of the harrow,

FIG. 9 is a plan view as seen in the direction indicated by an arrow IXin FIG. 8, and

FIG. 10 is a section, to an enlarged scale, taken on the line II--II inFIG. 1 but illustrates a still further alternative construction for someparts of the harrow.

Referring to FIGS. 1 to 5 of the drawings, those Figures illustrate arotary harrow which could also be considered as being a soil cultivatingimplement or cultivator. The harrow has a hollow box-shaped frameportion 1 that extends substantially horizontally transverse, andnormally substantially horizontally perpendicular, to the intendeddirection of operative travel of the harrow that is indicated by anarrow A in FIGS. 1, 2, 6, 8 and 10 of the drawings. A plurality (in thiscase, twelve) of vertical or substantially vertical shafts 2 arerotatably journalled in the hollow frame portion 1 and extend in asingle row in regularly spaced apart relationship. The longitudinal axesa (axes of rotation) of the shafts 2 are spaced apart from one anotherby distances which should not be greater than 30 centimeters and whichit is preferred should have magnitudes of substantially 25 centimeters.Each shaft 2 has a corresponding rotary soil working member 2A fastenedto its lowermost end that projects from beneath the frame portion 1 and,accordingly, the axes a are also the axes of rotation of the soilworking members 2A. The portion of each shaft 2 that projects frombeneath the frame portion 1 is splined (see FIG. 5) and receives asubstantially cylindrical boss at the center of a substantiallyhorizontally disposed tine support 3, the internal bore of said bossbeing splined to match the splines on the co-operating shaft 2, Theinterengaging splines ensure that the soil working member 2A is fast inrotation with its shaft 2 at all times, axial disengagement of the tinesupport 3 from the shaft 2 being prevented by tightening a fastening nut4, provided with a co-operating washer, onto a short lowermostscrewthreaded portion of the shaft 2 that extends beneath the splinedportion thereof. A split pin 5 is employed to prevent accidentalloosening of the nut 4. Two substantially cylindrical tine holders 6 arearranged at the opposite ends of each tine support 3 and receive thefastening portions 8 of rigid soil working tines 9 in a manner that willbe described in greater detail below. The longitudinal axis of each tinesupport 3 extends substantially perpendicular to the longitudinal axis aof the corresponding shaft 2 and it will be noted that each support 3,including the central boss thereof, the corresponding tine holders 6 andtwo screens 7, is formed integrally from a single piece of metallicmaterial by forging or casting.

It can be seen from FIG. 2 of the drawings, which is a view in adirection horizontally perpendicular to the longitudinal axis of thetine support 3 that is visible in that Figure, that, from such aviewpoint, the longitudinal axis of each sleeve-like holder 6 isinclined to the corresponding axis a by an angle a' which has amagnitude that it is preferred should not be less than 24°. Thelongitudinal axes of the two tine holders 6 that correspond to each soilworking member 2A thus diverge in an upward direction with the resultthat the opposite ends of the whole support 3 are further apart from oneanother at the top thereof than they are at the bottom thereof. Again asseen in FIG. 2 of the drawings, the opposite ends of the illustratedsupport 3 that are afforded by the two tine holders 6 are bevelleddownwardly from the top towards one another. As viewed in a directionparallel to the longitudinal axis of the support 3 (i.e. as seen in FIG.3 of the drawings), the longitudinal axes h of the tine holders 6 areboth non-perpendicularly inclined to the longitudinal axis of thesupport 3 in such a way that the top of each holder 6 is furtheradvanced with respect to the intended direction of rotation B (FIGS. 1,3 and 5) of the corresponding soil working member 2A than is the bottomthereof. As seen in FIG. 3 of the drawings, the longitudinal axis h ofeach tine holder 6 is inclined to the corresponding axis of rotation aat an angle β which preferably has a magnitude of substantially 8° andwhich it is preferred should not be less than substantially 8°.

The front of each tine support 3 with respect to the direction B has adownwardly and rearwardly inclined surface which merges with a similarlydisposed surface at the front of each holder 6. Although not strictlyparallel to the axes h, the front surfaces of the holder 6 with respectto the direction B may be considered as being substantially parallel tothe corresponding axes h. The top and front, with respect to thedirection B, of each tine holder 6 is provided with the previouslymentioned corresponding integral screen 7 which extends upwardly to alevel immediately beneath that of the bottom of the hollow frame portion1 (see FIGS. 2 and 3 of the drawings). The uppermost portion of eachscreen 7 is thus substantially horizontally disposed but the screen 7decreases in height, in a stepped manner, towards the corresponding axisa, to match the shape of a housing 8A for the lower bearing thatrotatably supports the corresponding shaft 2. The front of each screen 7with respect to the direction B is substantially, although not exactly,in line with the front of the corresponding tine holder 6 with respectto the same direction as will be evident from FIG. 3, in particular, ofthe drawings.

Each sleeve-like tine holder 6 receives the fastening portion 8 of acorresponding one of the soil working tines 9, each tine 9 alsoincluding a lower active or soil working portion 10. The fasteningportion 8 of each tine 9 has a first upwardly tapering part that is ofregular polygonal cross-section which commences at the level of theintegral junction between the portions 8 and 10 of the tine. This firstupwardly tapering part of the tine fastening portion 8 co-operates witha matchingly shaped part of the internal bore of the corresponding tineholder 6 and said first upwardly tapering part, at its upper end, joinsa second upwardly tapering part that has approximately three times theaxial length of the first upwardly tapering part but that is of muchless steeply tapering configuration. The second upwardly tapering partof the tine fastening portion 8 also co-operates with a matchinglyshaped part of the internal surface of the corresponding tine holder 6.The extreme upper end of the tine fastening portion 8 is formed as ashort screwthreaded portion of basically circular cross-section whichportion projects upwardly beyond the upper end of the co-operating tineholder 6 when the portion 8 is entered in that holder. A retaining nut11A is screwed onto the threaded end of the tine fastening portion 8 andhas a downwardly tapering frusto-conical lower surface which co-operatescentringly with a matchingly shaped mouth at the extreme upper end ofthe central bore through the corresponding tine holder 6.

At the junction between the fastening portion 8 and the active or soilworking portion 10 of each tine 9, said tine has a polygonalcross-section which, as illustrated in FIG. 4 of the drawings, ispreferably a regular hexagon. The active or soil working portion 10tapers gently from the level of FIG. 4 of the drawings to the lowermostfree end or tip of the tine and is of curved formation throughout amajor portion of its length which commences at its integral junctionwith the fastening portion 8. A free end or tip region of the active orsoil working portion 10 that is of shorter length than the curved regionis of substantially rectilinear configuration. The curved region of theactive or soil working portion 10 of each tine 9 has such a curvature,and the tine 9 is so arranged, that, from its junction with thecorresponding fastening portion 8, the active or soil working portion 10initially extends towards the corresponding axis of rotation a andtherefore, as seen in a direction horizontally perpendicular to thelongitudinal axis of the corresponding tine support 3 (i.e. as seen inFIG. 2 of the drawings), each active or soil working portion 10 isdisposed closest to the corresponding axis a at a location between itsopposite uppermost and lowermost ends. In the embodiment illustratedsaid location is significantly nearer to the upper end of each active orsoil working portion 10 than it is to the lower end thereof, saidportion 10 preferably having a length of substantially 25 centimeters.The distance between the free ends or tips of the two active or soilworking tine portions 10 that correspond to each soil working member 2Ais greater than the maximum distance between the opposite ends of thecorresponding tine support 3, which support 3 should be considered asbeing a tine mounting that includes the corresponding tine holders 6 andscreens 7. Each tine support 3 thus has a maximum length which is notmore than, and is preferably less than, the perpendicular distancebetween the longitudinal axes a of two immediately neighbouring shafts2.

Considered downwardly from the integral junction between the fasteningportion 8 and the active or soil working portion 10 of each tine 9, theactive or soil working portion 10 has a regular hexagonal cross-section(FIG. 4) which progressively changes into a rectangular cross-sectionand, when the rectangular cross-section is attained, the length ofdiagonals (as seen in cross-section) between the opposite cornersthereof change with flattening of the tine until, at and very near theextreme lowermost free end or tip thereof, the ratio between the lengthsof the two diagonals is substantially 2:1. The longer of the twodiagonals at this level is substantially tangential to a circle centeredupon the corresponding axis a. Each of the what would otherwise be foursubstantially flat sides of the active or soil working portion 10 ofeach tine 9 in a lowermost free end or tip region thereof is formed witha hollow recess or groove that commences at the extreme free end or tipthat extends upwardly along the tine therefrom. There are two recessesor grooves 11 in the sides of each tine portion 10 that face obliquelyforwards with respect to the direction B and two recesses or grooves 12in the sides thereof that face obliquely rearwards with respect to thedirection B, the leading recesses or grooves 11 having substantiallytwice the length along the tine 9 of the trailing recesses or grooves12. The leading longer recesses or grooves 11 have lengths which areeach equal to substantially one-third of the length of the correspondingactive or soil working tine portion 10.

In the embodiment which is being described, the tines 9 are constructedand are mounted in such a way that the center lines of their fasteningportions 8 and active or soil working portions 10 (it being rememberedthat these center lines are partially curved) are contained incorresponding single planes that are inclined to the axes a and thus,normally, to the vertical. As viewed in a horizontal directionperpendicular to the longitudinal axis of one of the tine supports 3(i.e. as seen in FIG. 2 of the drawings), the longitudinal axis of eachsubstantially straight free end or tip region of each active or soilworking tine portion 10 is substantially parallel to the longitudinalaxis h of the tine holder 6 that corresponds to the other tine 9 of thesame soil working member 2A. It will, of course, be realised that, whena tine 9 is fixed in its appointed position, the longitudinal axis ofits fastening portion 8 and the longitudinal axis h of the holder 6 inwhich that fastening portion 8 is lodged will be coincident. When therotary harrow is in operation, the tines 9 of neighbouring soil workingmembers 2A thereof work overlapping strips of soil to produce, ineffect, a single broad strip of worked soil.

FIG. 6 of the drawings illustrates the use of tines 12A that aresubstantially identical in construction and mounting to the previouslydescribed tines 9 except that the tines 12A have active or soil workingportions 13 each of which comprises two substantially straight regions14 and 15 that are interconnected by a corresponding sharply curvedpart. With this construction, the two portions 13 that correspond toeach soil working member 2A are closest to each other and to thecorresponding axis a, at a location between their ends. The free ends oftips of the two active or soil working portions 13 of each soil workingmember 2A are, as in the preceding embodiment, spaced apart from oneanother, and from the corresponding axis a, by a greater distance thanare the opposite ends of the tine support 3 or mounting which should beconsidered as including the holders 6 and screens 7 in that regard. Theangle which is enclosed between the longitudinal axes of the twostraight regions 14 and 15 of each active or soil working tine portion13 is equal, or substantially equal, to the angle a' that is enclosedbetween the longitudinal axis h of each tine holder 6 (and of thecorresponding tine fastening portion 8 when lodged in that holder) andthe corresponding axis of rotation a. Each upper straight region 14 hasa length which is equal to substantially one-quarter of the total lengthof the corresponding active or soil working tine portion 13, said lengthof the region 14 also being substantially one-third of the length of thecorresponding region 15.

FIG. 8 of the drawings illustrates the employment of tines 17 whosefastening portions 8 are adjoined by very short straight regions 18 ofactive or soil working portions 16 of the tines. As seen in a directionsubstantially horizontally perpendicular to the longitudinal axis ofeach tine support 3 (i.e. as seen in FIG. 8 of the drawings), thefastening portions 8 and the very short straight regions 18 of each tine17 are in longitudinal alignment with one another. The active or soilworking portions 16 also include much longer straight regions 19 thatintegrally adjoin the short straight regions 18 and that are outwardlydirected away from the axis a with their longitudinal axes inclined tothe longitudinal axes h of the fastening portions 8 and tine holders 6by an angle which is a little greater in magnitude than the angle a'.Once again, the distance between the free ends or tips of the two activeor soil working portions 16 of the two tines 17 of one soil workingmember 2A is not less, and is preferably a little greater, than thedistance between the extreme free ends of the corresponding tine support3. The tines 17 are otherwise substantially identical to the tines thathave been described above.

FIG. 10 of the drawings illustrates the provision of tines 20 which haveactive or soil working portions 19A that comprise three regions 21, 22and 23. The fastening portion 8 of each tine 20 is adjoined by theregion 21, which is a short straight region that is axially in line withthe fastening portion 8. The region 22 is also straight and isintegrally connected to the region 21 by a bend whose orientation issuch that the region 22 is inclined downwardly and outwardly away fromthe region 21 with respect to the axis a. The lowermost end of thestraight region 22 is integrally connected to the region 23, which is astraight free end or tip region, by a further bend, this latter bendbeing so dimensioned and orientated that the free end or tip region 23extends substantially longitudinally parallel to the axis a when thesoil working member 2A concerned is viewed in a direction substantiallyhorizontally perpendicular to the longitudinal axis of its tine support3 (i.e. as seen in FIG. 10 of the drawings). The free end or tip region23 of each tine 20 has a length which is equal to substantiallyone-third of the total length of the active or soil working portion 19Aof that tine, the recesses or grooves 11 and 12 being formed in the freeend or tip region 23 at the front and rear thereof with respect to theintended direction of rotation B. Each straight region 22 has a lengthwhich is substantially half the total length of the corresponding activeor soil working portion 19 A and each short straight region 21 has alength which is substantially half that of the corresponding free end ortip region 23. The longitudinal axis of each straight portion 22 isparallel or substantially parallel to the longitudinal axis h of thefastening portion 8 of the other tine 20 of the same soil working member2A. It will be remembered that, when one of the tine fastening portions8 is installed in the corresponding tine holder 6, the longitudinal axesof both that fastening portions 8 and the corresponding holder 6 arecoincident. The free ends or tips of the two tines 20 of each soilworking member 2A are, in the embodiment of FIG. 10 of the drawings,spaced apart from each other by a distance which is greater than thedistance between the axes a of two immediately neighbouring shafts 2.

Referring again to FIGS. 1 and 2, in particular, of the drawings, itwill be seen that the opposite ends of the hollow frame portion 1 carryvertical sector plates 24 that both extend substantially parallel to thedirection A. The fronts of the two sector plates 24 with respect to thedirection A carry substantially horizontally aligned pivots 25 aboutwhich arms 26, that extend rearwardly from said pivots 25 with respectto the direction A, are upwardly and downwardly turnable alongside thecorresponding sector plates 24. The rearmost edge of each sector plate24 is formed with a curved row of holes 28 in which each hole isequidistant from the axis defined by the pivots 25 and the correspondingarm 26 is formed with a single hole that can be brought into registerwith any chosen one of the holes 28 by turning the arm to an appropriateangular setting about the corresponding pivot 25. Horizontal bolts 27are provided for entry through the single holes in the arms 26 and theholes 28 that are chosen to retain the arms 26 in corresponding angularsettings about the pivots 25 with respect to the hollow frame portion 1.A rotatable supporting member 29 in the form of a ground roller isrotatably mounted about a substantially horizontal axis between therearmost downwardly orientated ends of the two arms 26, said groundroller being of open, rather than closed, substantially right circularcylindrical configuration and being arranged to extend throughoutsubstantially the whole of the working width of the soil working members2A. It will be appreciated that the angular setting of the arms 26 aboutthe pivots 25 which is chosen determines the level of the axis ofrotation of the supporting member 29 relative to the remainder of theharrow and is thus an important factor in determining the depth ofpenetration of the tines of the soil working members 2A into the groundduring operation of the harrow.

An upper front, with respect to the direction A, region of each sectorplate 24 is formed as an integral supporting plate 29 A (FIG. 2) and therear of each of those supporting plates carries a substantiallyhorizontal pivot 30, the two pivots 30 being in aligned relationship. Anangular supporting arm 31 is turnable about each pivot 30 alongside thecorresponding supporting plate 29A it being one straight limb 32 thereofwhich is disposed alongside the plate 29A and which, as a concequence,extends substantially parallel to the direction A. The axis defined bythe pivots 30 is substantially parallel to that defined by the pivots 25and is thus substantially horizontally perpendicular to the direction A.The leading end of each straight limb 32 with respect to the direction Ais bent over downwardly to join the other straight limb 33 of the samesupporting arm 31 which limb, sas seen in FIG. 2 of the drawings, isinclined downwardly, and forwardly by a few degrees with respect to thedirection A, from its curved junction with the limb 32. The lowermostfree ends of the straight limbs 33 of the two angular supporting arms 31carry substantially horizontally aligned stub shafts 34 around which asupporting member 35, in the form of a right circular cylindricalroller, is rotatable. It will be noted that, in other embodiments, thesupporting member at the front of the harrow is not necessarilyrotatable nor is its cylindrical configuration necessarily of circularcross-section. The greatest width of the supporting member 35 in thedirection A which, in this case, is also its diameter, is substantiallyequal to, or greater than, the distance between the axes a of twoimmediately neighbouring shafts 2. The same dimension of the supportingmember 35 is also substantially equal to the length of the active orsoil working portion 10 of one of the corresponding tines 9 and it willbe remembered that both this length and the distance between immediatelyneighbouring axes a has been stated to have a preferred magnitude ofsubstantially 25 centimeters.

The supporting member 35 extends throughout substantially the whole ofthe working width of the rotary harrow and it will be seen from FIG. 2of the drawings that it is located completely in front, with respect tothe direction A, of the hollow frame portion 1 apart from a narrowoverlying edge region of that frame portion. The rotatable supportingmember 35 can have its axis of rotation set at any chosen one of anumber of different levels relative to the remainder of the harrow byturning the angular supporting arms 31 upwardly or downwardly alongsidethe supporting plates 29A to bring single holes in the straight limbs 32thereof into register with chosen holes 37 in curved rows of those holesthat are formed near the front edges of the supporting plates 29A withrespect to the direction A at equal distances from the axis defined bythe pivots 30. Horizontal bolts 36 are provided for entry through thesingle holes in the arms 31 and the chosen holes 37 to retain those armsin corresponding angular settings about the pivots 30 and thus to retainthe axis of rotation of the supporting member 35 at a correspondinglevel relative to the remainder of the harrow. It will be noted that, inthe position illustrated in FIG. 2 of the drawings, the level of thestub shafts 34 and thus the level of the axis of rotation of thesupporting member 35 is substantially the same as the level of theretaining nuts 11A that maintain d the fastening portions 8 of the tines9 firmly in their holders 6. The bottom of the supporting member 35 thatis in engagement with the ground surface is located at a level beneaththat of the bottoms of the tine holders 6. The lower half of that regionof the external surface of the supporting member 35 that faces the soilworking members 2A is progressively further from a plane A--A (FIG. 2)that is parallel to a plane containing the longitudinal axes a of all ofthe shafts 2 of the single row of those shafts as one moves downwardlyalong that surface towards the ground. A plane that is tangential to theregion concerned near the center thereof is inclined to the plane A--Aby an angle γ whose magnitude is substantially 20°. The magnitude of theangle γ is changed when the level of the axis of rotation of thesupporting member 35 is altered by entering the bolts 36 throughalternative holes 37. It will, of course, be realised that the distancerelationship between the region of the external surface of thesupporting member 35 that faces the soil working member 2A and the planeA--A is also true for the plane which contains the axes a of the singlerow of shafts 2.

Two shield plates 38 that are normally substantially verticallydisposed, and that extend substantially parallel to the direction A, arearranged immediately beyond the opposite ends of the single row of soilworking members 2A, said shield plates 38 being coupled by arms topivotal mountings on top of the frame portion 1 in such a way that theycan turn upwardly and downwardly about the axes defined by those pivotalmountings to match undulations in the surface of the soil over whichtheir lower edges slide during the use of the rotary harrow. The shieldplates 38 serve partly to prevent or minimise ridging of the soil at theedges of the broad strip thereof that is displaced by the soil workingmembers 2A during the operation of the harrow and partly to preventstones and other potentially injurious articles from being flunglaterally of the path of travel of the harrow by its rapidly moving soilworking tines. A central region of the front of the frame portion 1 withrespect to the direction A is provided with a coupling member or trestle39 of generally triangular configuration. As illustrated in outline inFIG. 1 of the drawings, the coupling member or trestle 39 is employed inconnecting the frame of the harrow to the three-point lifting device orhitch at the rear of an agricultural tractor or other vehicle whichmoves and operates the harrow during its use. One of the shafts 2 of thecenter pair of soil working members 2A has an upward extension into agear box 40 that is mounted on top of the frame portion 1. The shaftextension that is located inside the gear box 40 is in driven connectionwith a rotary input shaft 42 of that gear box through the intermediaryof bevel pinions and a change-speed gear 41 mounted at the back of thegear box. The change-speed gear 41 comprises a plurality ofinterchangeable and/or exchangeable pinions of which a pair can beselected to enable a corresponding transmission ratio between the rotaryinput shaft 42 and a further parallel shaft within the gear box 40 to beemployed thus enabling the shafts 2 to be rotated at different speeds inresponse to an unchanged speed of rotation applied to the rotary inputshaft 42. The rotary input shaft 42 has a splined or otherwise keyed endthat projects forwardly from the gear box 40 is substantially thedirection A and that end is arranged to be placed in driven connectionwith the power take-off shaft of an agricultural tractor or otheroperating vehicle by way of an intermediate telescopic transmissionshaft 43, which is of a construction that is known per se, havinguniversal joints at its opposite ends. It can be seen in FIGS. 1 to 3 ofthe drawings that each of the shafts 2 is provided, inside the hollowframe portion 1, with a corresponding straight- or spur-toothed pinion44 and that the teeth of each pinion 44 are in mesh with those of itsimmediate neighbour, or both of its immediate neighbours, in the singlerow of pinions 44. Thus, rotation of the shaft 2 and pinion 44 that aredirectly driven from the gear box 40 causes rotation of all of the othershafts 2, and corresponding soil working members 2A, in the directions B(FIGS. 1 and 5), each direction of rotation B being opposite to thedirection of rotation B of the immediately neighbouring soil workingmember 2A, or each of the two immediately neighbouring soil workingmembers 2A, in the single row thereof.

The rotary harrow that has been described with reference to FIGS. 1 to 5of the drawings is particularly, but not exclusively, suitable fordealing with soil that contains an above average proportion of stones.This suitability is obtained as a result of the particular tinestructure that is employed together with the form of mounting of thosetines. In this connection, it will be recalled that the uppermost endsof the substantially cylindrical tine holders 6 of each member 2A arefurther apart from one another, and thus from the corresponding axis ofrotation a, than are the lowermost ends thereof, said tine holders 6thus having surfaces that are inclined to the vertical from top tobottom in directions generally inwardly towards the corresponding axisa. The suitability of the harrow for dealing with very stony soil isfurther improved by arranging the upper ends of the holders 6 in advanceof the lower ends thereof with respect to the intended directions ofrotation B of the corresponding soil working members 2A. When one of thetine holders 6 strikes a stone during operation of the harrow, thatstone tends to be urged downwardly along the inclined leading surfaces(with respect to the direction B) of the holder 6 itself and its screen7. A stone that has been downwardly displaced in this way is mostunlikely to cause further trouble because, after initially extendingtowards one another, the active or soil working portions 10 of the twotines 9 of each soil working member 2A are inclined outwardly away fromeach other so that the lower regions thereof that penetrate displacinglyinto the ground are well spaced apart. The likelihood of stones jammingbetween the two tines 9 of a single soil working member 2A is thus solow that its occurrence is quite uncommon and does not constitute asignificant cause of operational stoppages. Since the screens 7 areshaped to match the lower surface of the frame portion 1 and thecorresponding bearing housings 8A, insufficient space is left betweenthose parts for any but the most unusually shaped stone to become jammedand even such a rare stone will usually be so thin that it will breakand fall away before any significant damage can be caused. The circularpaths described by the tine holders 6 at the ends of the supports 3 donot overlap each other to any appreciable extent and the tendency forstones to get jammed between the tine mountings of neighbouring soilworking members 2A is thus so low as to be insignificant.

The cylindrical roller which affords the supporting member 35 is locatedin front, with respect to the direction A, of the soil working members2A and occupies a position which is such that, during operation, itbears upon the surface of the soil over a distance, in the direction A,which is equal to not less than substantially the radius of the roller.There will, of course, be instants at which this relationship is nottrue, particularly when the harrow is operating on very arid and/orstony soil. The supporting member 35 has a levelling effect whichgenerally improves the operation of the harrow since large accumulationsof soil in front of the members 2A are avoided. On fields that have avery large number of stones, the supporting member 35 acts also toprotect the frame portion 1, the mountings of the tines 9 and theirfastening portions 8 from damage because said member 35 tends to pressdownwardly into the soil any loose stones which it meets lying upon thesurface of the ground before those stones are engaged by the soilworking members 2A. It is thus uncommon for the fastening portions 8 ofthe tines 9, their mountings or the frame portion 1 to come directlyinto contact with undisplaced stones. The tendency for stones to becomejammed between the rear of the supporting member 35 and the tinemountings (particularly the holders 6 thereof) is very low because, dueto the relationship between the lower region of the rearwardly facingouter surface of the supporting member 35 and the plane A--A (FIG. 2)that has been discussed above, any stone in this area can readily escapein a downward direction and the tine holders 6 will generally co-operatewith the rear of the supporting member 35 in pushing any stone in thisarea out of harm's way.

When the tines 12A shown in FIG. 6 of the drawings are employed,sufficient space is left between the tines of neighbouring soil workingmembers 2A for conducting away potentially damaging stones. This is alsotrue of the tines 20 provided in accordance with FIG. 10 of the drawingsand is correct in respect of the tines 17 of FIG. 8 although, in thelatter case, the spacing is not quite so large as with the otherembodiments. It will be noted that, when the tines 20 illustrated inFIG. 10 are employed, the free end or tip regions 23 of the active orsoil working portions 19A work overlapping strips of soil and, due totheir dispositions as compared with the dispositions of correspondingregions of the active or soil working portions of the other tines thathave been described, the actual lengths thereof that perform thisoperation are greater. It will be noted that it is possible to set theactive or soil working portions of the tines in operating positions thatare different to those illustrated in the drawings by temporarilyloosening the nuts 11A, turning the fastening portions 8 throughappropriate angles about the axes h and finally re-tightening the nuts11A. With the construction that has been described, an angulardisplacement about the axis h of 60°, or a multiple of 60°, is necessary(see FIGS. 2 and 4 of the drawings).

Although effective protection of the fastening portions 8 of the tinesand of the mountings of those tines is provided by the constructions andarrangements thereof that have been described, an important improvementin this protection resides in the provision of a supporting member infront of the soil working members 2A, particularly when the rotaryharrow is to be employed for working soil that contains a highproportion of stones. It is pointed out, in this connection, that thesupporting member also protects the front of the frame portion 1 withrespect to the direction A, it clearly being necessary that the frameportion 1 should not be seriously damaged by stones and other hardarticles if the harrow is to function correctly.

FIGS. 6 and 7 of the drawings illustrate the provision of the rotaryharrow with a supporting member 45 that is of cylindrical constructionbut not of circular cross-section. The supporting member 45 is disposedat the front of the rotary harrow with respect to the direction A and issuspended from at least two spaced supports 46 mounted on top of theframe portion 1. Each support 46 is of channel-shaped cross-section andis disposed with its base in contact with the top of the frame portion 1and its limbs directed upwardly therefrom. Each support 46 extendssubstantially parallel to the direction A and projects beyond the frontof the frame portion 1 with respect to that direction. The forwardlyprojecting portion of each support 46 carries a corresponding pivot pin47, the pivot pins 47 being substantially horizontally aligned in adirection parallel to the row of soil working members 2A and thus,normally, substantially perpendicular to the direction A. Thesubstantially flat top 49 of the supporting member 45 carries as manypairs of lugs 48 as there are supports 46 and each pair of lugs 48 isturnably connected to the corresponding support 46 by the correspondingpivot pin 47. The supporting member 45 extends throughout substantiallythe whole working width of the harrow and its longitudinal axis isparallel or substantially parallel to a plane containing all the axes aof the single row of shafts 2. Although the top 49 of the member 45 issubstantially flat, a considerable part of its cross-section is ofcurved configuration and the maximum width of that cross-section extendsin the same general direction as the direction A. The flat top 49 isnormally inclined to the horizontal in such a way that, as can be seenin FIG. 6 of the drawings, said top extends upwardly from rear to frontwith respect to the direction A. The rearmost edge of the flat top 49takes the form of a downwardly directed angular bend beneath which thereis a flat stop portion 50 which normally, as illustrated in FIGS. 6 and7, bears against an abutment surface formed by a front region of themain frame portion 1. The lowermost edge of the flat stop portion 50 isbent over angularly forwards with respect to the direction A to form anarrow flat portion 51 that is directed downwardly and forwardly fromthe portion 50 with respect to the direction A. The lowermost edge ofthe narrow flat portion 51 is, in turn, bent back angularly to form abroad flat portion 52 that extends down to the bottom of the supportingmember 45. The lowermost edge of the broad flat portion 52 is atsubstantially the same horizotal level as the bottoms of the tineholders 6 and said portion 52 extends parallel, or approximatelyparallel, to the axes h of those holders 6 when the latter are in theirpositions of furthest advancement with respect to the direction A aroundthe axes a. The bottom of the supporting member 45 that extendsforwardly from the lowermost edge of the portion 52 is afforded first bya substantially flat or very gently curved portion 53 that is orientatedforwardly and upwardly and, secondly, by a leading curved portion 54whose uppermost edge coincides with the leading edge of the flat top 49.

In the use of the rotary harrow as illustrated in FIGS. 6 and 7 of thedrawings, the cylindrical supporting member 45 can pivot freely aboutthe axis defined by the pins 47 within the limits defined by the flatstop portion 50 thereof and abutment of the flat top 49 against bevelledleading edges of each support 46. During operation under average workingconditions, the supporting member 45 bears upon the ground surfacethroughout a width, in the direction A, that is substantially equal tothe radius of a circle whose diameter is the same as the maximumcross-sectional diameter of the member 45 as seen in FIG. 6 of thedrawings. This diameter is substantially equal to the maximum width ofthe member 45 as measured in the direction A and is also substantiallyequal to the distance between two neighbouring axes a and to the lengthof the active or soil working portion 13 of a single one of the tines12A.

In the embodiment of FIGS. 8 and 9 of the drawings the rotary harrow hasa supporting member 55 which, like the supporting member 35, is of rightcircular cylindrical configuration but which is angularly adjustable,rather than rotatable, about substantially horizontally aligned stubshafts 56 relative to upright arms 57. The arms 57 have their upper endspivotally connected to arms 59 by strong substantially horizontallyaligned pins 58. The arms 59 are integral with the sector plates 24 andare located at the top and front of those sector plates with respect tothe direction A. Each of the arms 57 extends through a slot in acorresponding bracket 60 that is fastened to the top of the frameportion 1. Each arm 57 is thus turnable to a limited extent about thecorresponding pivot pin 58 within the limits that are defined by theopposite ends of the slot in the corresponding bracket 60. The oppositeedges of each slot also serve a guiding function for the correspondingarm 57. Each arm 57 is also turnably connected to one end of acorresponding rod 62 by means of a pivot pin 61 that is afforded by thebent-over end of the rod 62 concerned. Each rod 62 is axially slidablethrough an eye 63 carried by the corresponding arm 59 and carries a stopring 64 at or near the end thereof that is remote from the correspondingpivot pin 61. A helical compression spring 65 is wound around each rod62 so as to bear between the corresponding eye 63 and corresponding stopring 64 and it will be evident from FIG. 8 of the drawings that thesprings 65 urge the arms 57 and the supporting member 55 which thosearms carry in an anticlockwise direction, as seen in FIG. 8, about theaxis defined by the pivot pins 58. The arms 57 normally bear againststops defined by the rearmost ends of the slots in the brackets 60. Theopposite ends of the supporting member 55 are secured to the arms 57 bybolts 66 and the member 55 can occupy any chosen one of four differentangular settings about the axis defined by the stub shafts 56 relativeto the arms 57 by temporarily removing the bolts 66, making the requiredangular adjustment, and subsequently replacing those bolts.

The supporting member 55 operates in a very similar manner to thepreviously described supporting member 35 except that, incontradistinction to the member 35, it does not revolve duringoperation. However, in this case, if at least one stone or otherpotentially damaging hard article should get in between the member 55and one or more tine mountings, the member 55 can yield pivotablyforwards about the axis defined by the pivot pins 58 against the actionof the compression springs 65. That region of the member 55 whichcontacts the ground surface will, of course, inevitably be subject towear and, when it has become worn to an unacceptable extent, the bolts66 may be temporarily removed and the member be turned through 90° aboutthe axis defined by the stub shafts 56 to bring a fresh substantiallyunworn region of the member 55 into a position in which it will contactthe ground. The bolts 66 are then replaced. The useful life of themember 55 can thus be considerably prolonged.

FIG. 10 of the drawings illustrates the provision of a cylindricalsupporting member 67 that is of substantially square cross-section. Itwill be evident from a comparison between FIGS. 8 and 10 of the drawingsthat the non-rotatable member 67 is mounted substantially the sme way asthe member 55 although the different cross-sectional shape of the member67 necessitates some consequential alteration in the shapes of the arms57 and brackets 60. The supporting member 67 is arranged so that, asseen in cross-section (FIG. 10) a diagonal between two of its oppositecorners is substantially vertical while a diagonal between its oppositetwo corners is substantially horizontal. The arms 57 again normally bearagainst the stops that are afforded by the rearmost ends of the slots inthe brackets 60 but said arms 57 may also normally bear against aleading upper edge region of the main frame portion 1. This is also trueof the embodiment of FIGS. 8 and 9 of the drawings. In the embodiment ofFIG. 10, the angle γ has a magnitude of substantially 45° and ismeasured between the plane A--A and the flat lower surface of thesupporting member 67 that faces rearwardly towards the soil workingmembers 2A. The angle is measured at a level which is the same as, orjust beneath, the level of the axis defined by the stub shafts 56. Thenon-rotatable supporting member 67 operates in a very similar manner tothe previously described supporting member 55 but the large downwardlyopening angle γ that results from the square cross-section and from themounting of the member 67 ensures that there is a large space availablefor guiding away any stones which might tend to get jammed in this area.The sharp downwardly directed corner of the square cross-sectionsupporting member 67 is particularly effective in levelling a strip ofsoil immediately before that soil is worked by the tines 20. Once saidedge is worn to an unacceptable extent, it is only necessary temporarilyto remove the bolts 66, to turn the member 67 through 90° about the axisdefined by the stub shafts 56 and to replace the bolts 66 to bring a newsubstantially unworn edge into the lowermost operative position.

Although certain features of the rotary harrows that have been describedand/or that are illustrated in the accompanying drawings will be setforth in the following claims as inventive features, it is emphasisedthat the invention is not necessarily limited to those features and thatit includes within its scope each of the parts of each rotary harrowthat has been described and/or that is illustrated in the accompanyingdrawings both individually and in various combinations.

What we claim is:
 1. A rotary harrow comprising a frame portionsupporting a number of soil working members rotatably mounted in atransverse row on upwardly extending shaft means, each of said soilworking members including a generally horizontal support of elongateconfiguration and a sleeve-like tine holder at each end thereof, adownwardly extending tine being held in an internal bore that extendsthrough the top and bottom of said holder, said support being rotatableabout an axis of rotation defined by said shaft means that issubstantially centrally located between the holders on said support, thetop of said holder being radially spaced further from said axis ofrotation than the bottom thereof at the outer side of that holder, theouter surfaces of said holder being substantially inclined to said axisof rotation.
 2. A harrow as claimed in claim 1, wherein said holder isgenerally cylindrical and the longitudinal axis of said bore is inclinedto said axis of rotation whereby said bore adjacent the top of theholder is spaced further from that axis than at the bottom of thatholder.
 3. A harrow as claimed in claim 1, wherein said holder isgenerally cylindrical and said bore is inclined to said axis ofrotation, the top of said holder being further advanced with respect tothe normal direction of rotation of said soil working member than is thebottom of that holder.
 4. A harrow as claimed in claim 3, wherein thefront of said holder has an outer surface that is inclined downwardlyand rearwardly with respect to said normal direction of rotation.
 5. Aharrow as claimed in claim 4, wherein said support and its correspondingholders are formed from an integral piece of metal.
 6. A harrow asclaimed in claim 1, wherein an integral screen at the top of said holderis positioned at the front of that holder with respect to the normaldirection of rotation, said holder with an adjacent part of said supportcomprising a tine mounting and said screen having a leading outersurface substantially in line with the front surface of said holder withrespect to said direction of rotation, said screen being located closelyadjacent the bottom of said frame portion.
 7. A harrow as claimed inclaim 6, wherein the vertical extent of each screen above said mountingdecreases in a direction towards said axis of rotation.
 8. A harrow asclaimed in claim 1, wherein said soil working portion of each tine iscurved from its junction with the corresponding fastening portion,towards a lower tip of the tine, the curved region of said portionmerging, at a distance from said tip, into a substantially straightregion of said soil working portion.
 9. A harrow as claimed in claim 8,wherein the longitudinal axis of the substantially straight region ofsaid soil working portion is substantially parallel to the longitudinalaxis of the fastening portion of a second tine of the same soil workingmember.
 10. A harrow as claimed in claim 9, wherein said soil workingportion extends closest to said axis of rotation at a locationsubstantially one-quarter along the length of said soil working portionfrom its junction with the corresponding fastening portion.
 11. A harrowas claimed in claim 1, wherein the soil working portion of each tinecomprises two relatively inclined straight regions.
 12. A harrow asclaimed in claim 11, wherein the lengths of said two straight regionsare in the ratio of about 1 :
 3. 13. A harrow as claimed in claim 12,wherein a shorter straight region adjoins said fastening portion.
 14. Aharrow as claimed in claim 11, wherein the soil working portions of twotines of said soil working member extend closest to said axis ofrotation immediately beneath said support.
 15. A harrow as claimed inclaim 11, wherein said two substantially straight regions are ofdissimilar lengths, and the longer straight region terminates at adistance from the lower tip of the corresponding tine and adjoins afurther region of the soil working portion which extends substantiallyparallel to said axis of rotation.
 16. A rotary harrow comprising anumber of soil working members arranged in a row that extends transverseto the direction of travel and each member being rotatably mounted on acorresponding upwardly extending shaft, said member including agenerally horizontal support of elongate configuration and a sleeve-liketine holder at each end thereof, a downwardly extending tine being heldin said holder and said support being rotatable about an axis ofrotation defined by said shaft that is substantially centrally locatedbetween the holders of said support, each holder and part of eachsupport located between the holder and said axis of rotation, comprisinga tine mounting that has a front leading surface with respect to thenormal direction of rotation of the corresponding soil working member,the top of said leading surface being inclined forwardly in saiddirection of rotation in advance of the bottom thereof.
 17. A harrow asclaimed in claim 16, wherein, when viewed in a horizontal directionperpendicular to the length of each tine mounting, the longitudinal axisof each corresponding tine holder is inclined to said axis of rotationat an angle of not less than about 24°.
 18. A harrow as claimed in claim16, wherein when viewed lengthwise of each tine mounting, thelongitudinal axis of the corresponding tine holder is inclined to saidaxis of rotation at an angle of not less than about 8°.
 19. A harrow asclaimed in claim 16, wherein considered from said axis of rotation to anouter end of each tine mounting, the corresponding mounting exhibits aleading surface which is inclined to the vertical and to the horizontalfrom top to bottom with respect to said normal direction of rotation.20. A harrow as claimed in claim 16, wherein the longitudinal axis ofeach tine holder is substantially parallel to the leading surface of thecorresponding mounting with respect to said direction of rotation.
 21. Aharrow as claimed in claim 16, wherein the overall radial length of eachtine mounting, considered from said axis of rotation, is not greaterthan half the distance between the axis of rotation of two immediatelyadjacent soil working members.
 22. A rotary harrow comprising aplurality of rotatable soil working members positioned side-by-side in atransverse row, each of said members including a substantiallyhorizontally elongated support with a sleeve-like tine holder adjacenteach opposite end thereof, said support being rotatable about anupwardly extending shaft and said shaft being located substantiallymidway between the holders of said support, each holder and an adjacentsupport part comprising a tine mounting that extends radially from oneside of said shaft, the radial length of said mounting being not greaterthan half the distance between the shafts of two immediatelyneighbouring soil working members, a downwardly extending tine in saidholder and said tine having a fastening portion that is secured with thetop thereof positioned forwardly of the remainder of said portion withrespect to the normal direction of rotation of said soil working member,said mounting having a leading surface that is inclined andsubstantially parallel to said fastening portion.
 23. A harrow asclaimed in claim 22, wherein said tine has an elongated soil workingportion which, when the corresponding soil working member is viewed inside elevation and in a direction along the length of said support, hasa longitudinal axis substantially in alignment with the longitudinalaxis of said fastening portion.
 24. A harrow as claimed in claim 23,wherein said soil working portion comprises two relatively inclinedstraight regions, said two regions being of dissimilar length and alonger length region terminating at a distance from a lower tip of thecorresponding tine and said longer length region adjoining a furtherregion of said soil working portion which extends substantially parallelto said axis of rotation.
 25. A harrow as claimed in claim 23, whereinthe lower tips of the soil working portions of two tines of each soilworking member are further spaced apart from one another than are theopposite ends of the same portions that adjoin their correspondingfastening portions.
 26. A harrow as claimed in claim 23, wherein lowertips of the soil working portions of two tines of each soil workingmember are spaced apart from one another by a greater distance than arethe upper opposite ends of their corresponding fastening portions.